1. Field of the Invention
The present invention relates to an a sonic toothbrush appliance and charging base.
2. Background Art
Power-operated toothbrushes have long been used to make the task of toothbrushing easier and more convenient. Older power toothbrushes required excessive movement of the brush head to obtain effective cleaning. Excessive movement of the brush head could potentially injure the gums and soft palette of a user.
Ultrasonic toothbrushes have been developed that move a toothbrush head reciprocally or in an oscillating path by means of a rotating linkage or other drive mechanism. One example of an ultrasonic toothbrush is disclosed in U.S. Pat. No. 5,378,153 to Giuliani et al. The Giuliani patent specifies a bristle tip velocity in excess of 1.5 meters per second (m/s) that is extremely vigorous and may be excessive for some individuals.
Products made in accordance with the Giuliani patent may also utilize a brushing head that requires two expensive rare earth magnets on the replaceable brush component that must be thrown away when the brush head is replaced. The use of rare earth magnets on a replaceable component unnecessarily adds to the cost of the replaceable brush element. The extremely high loading necessitated by the geometry of the torsion bar used in the Giuliani device requires that it be made of an expensive alloy such as beryllium-copper-titanium. The torsion bar is also disposed of when the brush head is replaced adding considerable cost to the replacement brush.
Further, user assembled component parts of the Giuliani patent include critical components that require maintaining spacing between parts that are assembled by the user. The brush head is a user assembled part that is disposable and must often be replaced. If anything sticks to the magnets of the disposable brush head, it can cause rubbing or contact problems. The Giuliani device is also sensitive to dirt, mis-handling, improper installation, manufacturing problems, and product variation from required manufacturing tolerances. If there are changes in the manufacturing standards for a brush head, the brush head may not work with an older toothbrush drive due to the arrangement of the critical components in the Giuliani product.
These and other problems and disadvantages associated with prior art power toothbrushes are addressed by Applicant""s invention that provides a sonic toothbrush that operates at a safe and effective level while allowing for the use of a low cost replaceable brush head that is easy for a user to replace and does not require the user to assemble critical parts having close tolerance requirements.
According to the present invention, a sonic toothbrush is provided that features a replaceable toothbrush head that is driven by a torsion bar that is anchored at one end and moved in an arcuate rotary motion about the brush shaft axis. The motion closely approximates the brush action recommended by the American Dental Association. Rotary movement of the torsion bar is generated by providing an electromagnet on a core in the handle of the toothbrush that acts upon a pair of magnets secured to a magnet plate that is in turn secured to the torsion bar that is fixed at one end to the handle.
According to one aspect of the invention, an electric toothbrush is provided that includes a brush head assembly, a housing, and a frame enclosed by the housing. A power supply is contained within the housing and an electric coil is secured to the frame and electrically connected to the power supply through a control circuit that creates an alternating flow of current in the coil. The brush head assembly is connected to a distal end of an elongated shaft. The elongated shaft has an internal end that is disposed within the housing. A torsion bar is secured to the frame at the first end. An armature is connected to a second end of the torsion bar and the internal end of the elongated shaft. First and second magnets are arranged on the armature. The magnets are in line generally in a plane that is parallel to a central access of the shaft. The alternating flow of current in the electric coil alternates at a predetermined frequency to cause the magnets to be alternately attracted to the coil thereby causing the torsion bar to twist and the shaft to oscillate in the desired oscillatory rotary motion.
According to another aspect of the invention, the frame is a one piece die casting to which the coil, torsion bar and bearing journaling the internal end of the shaft are secured. A torsion bar is preferably clamped by an anchoring plate to the frame at its first end. A bearing journals one end of the elongated shaft for oscillating rotary movement and inhibits translation movement.
According to another aspect of the invention, the brush head assembly is supported on a detachable shaft that is detachable from the elongated shaft. Further, the brush head assembly may be detached from the elongated shaft without opening the housing and without affecting the coil and magnets.
According to yet another aspect of the invention, the torsion bar is secured to the armature between the first and second magnets. The elongated shaft is connected at its internal end to the armature. The armature supporting the first and second magnets has a flat plate portion on which the first and second magnets are disposed and a flange extending perpendicularly relative to the flat plate portion. The elongated shaft is secured to the flange. The coil may be formed on an e-shaped coil armature.
According to a further aspect of the invention, a charging coil is contained within the housing for recharging the power supply contained in the housing. The toothbrush may be provided in combination with a charging base wherein a charging circuit is provided to charge the batteries and wherein placing the electric toothbrush in the base ends an operating cycle of the toothbrush.
According to another aspect of the invention, the toothbrush may have a single control switch that is depressed multiple times to select one of a plurality of operational speeds. A plurality of LEDs are used to indicate the speed of the brush operation.
According to another aspect of the invention, an electric toothbrush is provided that includes a handle enclosing an electric coil that oscillates the driveshaft about a longitudinal axis. The driveshaft may be formed in one or two pieces. If it is formed in one piece, the driveshaft is secured to the handle at an inner end and extends through a bearing to a coupler that connects an outer end to a driven shaft that is part of a detachable brush head assembly. The driveshaft may also be formed in two pieces including a torsion bar and a cylindrical shaft that is aligned axially with the torsion bar. The torsion bar is connected on its inner end to the handle and is connected at its opposite end to the cylindrical shaft. The cylindrical shaft is received in a bearing supported by the handle. A cylindrical shaft pivots arcuately relative to the handle. The brush head assembly is removably secured to the handle. The brush head assembly has a driven shaft that is operatively secured to the cylindrical shaft and is pivoted arcuately by the shaft.
According to another aspect of the invention, the driveshaft is mounted in a bearing having the primary function of eliminating translational motion and allowing primarily only rotary motion.
The sonic toothbrush has multiple amplitude settings and corresponding LED speed indicators. The sonic toothbrush is microprocessor controlled and includes a timer that signals or stops operation of the toothbrush when a predetermined interval of time has passed to assure adequate brushing.
According to the invention, all the critical components of the sonic toothbrush are secured within the handle of the sonic toothbrush so that they are not accessible to the user. The user may change the brush head without opening the handle. The connection between the brush head and the handle is not a close tolerance fit and may be easily performed by a user.
The brush velocity is limited to substantially less than 1.5 meters per second. By limiting the brushing rate, an effective yet comfortable sonic toothbrush is provided with acceptable noise and vibration levels.